Hereinafter, a background art and a problem thereof will be described with reference to drawings.
FIG. 1 is an internal cross sectional view for explaining a conventional fuel injection pump, and referring to FIG. 2, a general conventional fuel injection pump includes a pump casing 10, a barrel 11, and a plunger 12.
The pump casing 10 of the conventional fuel injection pump configured as above has a barrel insertion groove 100 formed thereinside and a fuel input hole 102 connected to a fuel inlet penetrates through a center portion of an outer circumference thereof so as to be connected to the barrel insertion groove 100.
The barrel 11 is mounted to the barrel insertion groove 100 of the pump casing 10, and a fuel relief plug 110 is installed on a center portion of an outer circumference thereof so as to connect the fuel inlet hole 102 and a plunger coupling hole 111 formed inside.
The plunger 12 is slidably coupled to the plunger coupling hole 111 of the barrel 11 so that a lower portion thereof is protruded outwardly from the barrel 11 and a lower portion of the pump casing 10.
The general fuel injection pump of a diesel engine configured as above injects fuel by the plunger 12 respectively installed on each cylinder. Thus, fuel injection may have a combustion pattern corresponding to one cycle by a cam, and only a volume is determined in the plunger 12, and it is not possible to control the value of the volume during an operation in order for fine injection and incomplete combustion prior to combustion, thereby requiring an additional variable fuel injection timing adjustment apparatus in order to change a fuel injection timing during the operation. In other words, in case of a mechanic type apparatus, the injection timing is adjusted by moving the barrel 11 inserted thereinside upward and downward, and, in case of an electronic type, a crank angle is read in a form of a common rail to perform the fuel injection at a required timing.
However, a variable fuel injection timing apparatus as above is very expensive, and adjustment or control thereof is very difficult. In addition, only a volume of fuel can be controlled by forming a spiral groove (helices) on the plunger 12 such that a main volume of engine injection fuel is injected in only a predetermined pattern.
Also, in the conventional fuel injection pump as above, because one cycle is formed by only one plunger 12 in the pump, any different combustion pattern cannot be implemented without an additional apparatus. Also, because a fuel amount and the injection timing should be adjusted by one plunger 12, it is difficult to form various fuel injection patterns. Such pattern has a problem in that an engine operation as well as a fuel change and a timing thereof need to be adjusted very carefully during an operation, and it is difficult for every load area to show an optimal performance because all areas of an engine load are coped with one plunger 12 within one fuel injection pump, and a load is not actively coped with, thereby causing a problem of fuel efficiency and a problem of harmful gas discharge.